Process of treating silk and silk products



Patented F eb. 4, 1936 UNITED STATES PATENT" OFFICE PROCESS OF TREATING SILK AND SILK PRODUCTS Leo Wallerstein, Thomas Hawley, and Rowland A. Gale, New York, N. Y., assignors to Wallerstein Company, Inc., New York, N. Y., a corporation of New York No Drawing Application April 19, 1932,

Serial No. 606,286

9 Claims.

This invention relates to a process or method of improving silk containing its natural gum prior to fabrication or other textile operations such as weaving, throwing, knitting, and so species of silk worms consists of threads or filaments which are coated or surrounded by a natural gummy material or gum which is mainly composed of ajsubstance known as sericin.

In the manufacture of silk products, such as knitted or woven fabrics made of silk or in which silk is a component part this gum is nearly always removed, which is usually done from the finished product, that is to say, from the woven or knitted fabric. This has usually been effected by boiling in a soap solution, or treatment in solutions or baths which are alkaline at temperatures closely approaching a boil. and as a general rule this degumming is done after the knitting or weaving processes, as above stated.'

These treatments, known as the boil-ofi, are frequently disadvantageous, in that the silk or fabric containing the silk must be subjected to the boil-off process for prolonged periods, with the result that the fabric may be damaged. This alkaline process for degumming silk, even at' temperatures below the boil, is particularly disadvantageous with fabrics containing silk and other fibers, for examples, cellulose acetate or wool, since wool and cellulose acetate lose many of their desirable properties when exposed -to the influence of the alkaline boil-oif bath, even at temperatures below the boiling point.

It has also been proposed to use'certain proteolytic and diastatic enzymes for degumming silk, the silk being subjected to the action of these enzymes to remove the sericin.

The construction of many knitted or woven fabrics is such that it is very difficult for degumming agents, either alkaline liquors or enzymes, to attack the gum. This difficulty in penetration may be due ,to such causes as tight twisting or other close packing of the silk fibers.

Onthe other hand, it is not considered advisable to remove the gum at an earlier'stage in the .processing since the action ,of the gum in strengthening and holding together the fibers is advantageous in many of the mechanical processes; Also, the presence of the gum during processing frequently has a desirable eflect on the finished product.

We have discovered, by treating or impregnating the raw silk with a protease preparation under suitable conditions prior to the above mentioned factors, such as tight twisting, which prevent thorough and even penetration and then 'drying the impregnated silk fiber, that the sericin is changed or modified without the removal from the fiber of any substantial amount of the gum, this modification of the sericin permitting a very easy and quick subsequent degumming,

The applicants first treat the silk containing its natural gum, commonly referred to as gum- 15 silk, with the proteolytic enzyme preparation. This treatment is practiced under such conditions that the gum is not removed. Without heating or otherwise processing, the silk is lifted from the solution and dried. This new dry enzyme-treated silk which now still retains the gum may now be stored for future use or it may be utilized in fabrication processes immediately. Actual degumming of thesilk is accomplished at -a later stage of manufacture.

Silk so treated can be processed in the same way as untreated silk. Such silk fibers, woven or knitted, or fabrics or yarns containing silk may be degummed by the usual methods in a much shorter time or with milder soap solutions, where soap is used, with much less damage to the silk fibers. This increased ease of gum removal makes simultaneous dyeing and degumming possible in many cases, as with silk yarns.

Furthermore, fabrics in which other materials, such as cellulose acetate or wool above referred to, are used with the silk can be degummed under conditions which do not injure these fabrics, as with a very mild soap solution, or evenby the use of hot water.

In short, a new type of silk has been produced by this process which, because of the ease by which it can be degummed, permits the production of new types of fabrics, as, for instance, finer wool yarn or thread may be used in .weaving with such silk andthe degumming effected without damage to the wool.

Various protease preparations may be used in carrying out the process, such as protease preparations derivedfrom micro-organisms which under suitable culture conditions develop proteolytic enzymes, as, for instance, preparations derived from Aspergillus oryzea, from cultivation of bacteria: such as belong to the group of mesentericus or subtilis. Other suitable proteolytic enzymes may be used, such ,as papain, trypsin,

Example 1.100 poundsof raw silk aresoaked from 30 minutes to 1 hour in-a bath or solution consisting of 400 pounds of water in which have been dissolved. 50 pounds of the bacterial enzyme preparation, 1 pound of sodium sulfite for efiecting a suitable pH, and 1 pound of a sulfonated oil, this latter material being used to effect a better penetration, or as it is technically called,

a wetting-out of the fiber, though it will be un-- derstood that other penetrants can be used for effecting this wetting-out, such as a small amount of soap. Other suitable pH regulators, for instance, sodium carbonate or bicarbonate. or a mixture of both may vbe used instead of the sodium sulfite referred to. Emulsions of common soaking oils, such as neats-foot oil, may also be used in conjunction with enzymes. The temperature at which this process is carried out may be advantageously varied with the time consumed in the operation, the nature or origin'of the silk, the nature of the particular enzyme employed, and the presence of other constituents, such as pH regulators. However, we generally employ this process at room temperature, that is, from 60 to 85 F. i

The silk is then removed from the enzyme bath and the adhering liquor is removed in any suitable manner, as by centrifuging, and after the centrifuging step the silk fibers are dried at a'- low temperature by an air blast or any other suitable method.

Ezample' 2.-100 pounds of 13/15 japan white silk in the gum are soaked for 30 minutes at room temperature in 400pounds of a water solution containing 5 pounds of papain, 4 pounds of sulfonated oil, 0.05 pounds-of potassium cyanide, 2 pounds of mono-sodium phosphate. It is then centrifuged and air dried.

Example 3.-100 poun s of 13/15 japan white silk in the gum are soake for'30 minutes at room temperature in 400 pounds of a water solution containing 5 pounds of pancreatin, and 1 pound fore referred to. ,After the silk has been processed as desired, it is easily and quickly degummedby subjecting it to a mild boil-off liquor containing soap or, where soap is objectionable, by

immersion in a warm of hot water bath.

The sericin is so modified by this treatment thatthe usual swelling during the boil-off is greatly reduced and the gum may be very quickly removed from the fiber',.so the process is of par- 'ticular advantage for fabrics which are difficult erate degumming operation, as above described, will lose only about 85% of its gum, which is a matter of some importance, as for certain pinposes it may be desirable to retain a small quantity of gum in the finished fabric.

With the raw silk treated as described, a wide variety of fabrics may be produced by using this treated silk in which the gum is retained in substantially the amount originally present in it, and such silk after mechanical processing may be degummed without substantial injury to it or to other fibers with which it may be associated.

It between the applicants process of treating gumsilk with enzymes and other processes of degumming silk with enzymes resides in the fact that the applicants invention relates to a new method of treating silk with proteolytic enzyme. to produce a silk which has entirely new and unforeseen properties and not to a process of degumming silk.

What is claimed is:

1. The process of treating raw silk coated or covered with its natural gum, so that its gum may be more readily removed subsequently, which process consists in impregnating the silk with a protease preparation, and drying the im-. pregnated silk without removal of any substantial amount of the silk gum.

2.'The provess of treating raw silk coated or covered with its natural gum, so that its gum may be removed more readily subsequently, which process consists in impregnating the silk with a protease preparation, drying the impregnated silk without removal of any substantial amount of the silk gum, processing the silk with the retained gum, and then removing the gum.

3. The process of treating raw silk coated or covered with its natural gum, so that item may be more readily removed subsequently, which process consists in impregnating the silk will be noted that an important distinction with a solution comprising a protease preparation of bacterial origin, water and a wetting-out agent, drying the impregnated silk without removal oi. any substantial amount of the silk gum, processing the silk as by weaving or knitting, and-v then removing the gum by immersing in a hot degumming bath.

4. A process of preparing silk covered by its natural gum for subsequent fabrication processes including winding, throwing, weaving, knitting, dyeing and so forth, so that'its gum may be more readilyremoved subsequently which comprises treating such silk with a proteolytic' enzyme preparation and carrying out this process at such temperatures as to prevent substantial degumming. i i

5. A process of treating silk containing its natural gum, which comprises soaking the silk for a period from 30 minutes to 1 hour in a bath of water containing a bacterial enzyme preparation, sodium sulfite and a sulfonated oil at a temperature from 60 to 85 F., 100 parts of said raw silk being utilized to about, every 450 parts of the bacterial enzyme preparation, 1 part of sodium sulfite and 1 part of sulfonated oil, then removing the silk; from saidbath, removing and separating the adhering liquor and then dryin the. silk fibers at a low temperature, said parts being by weight. I

6. A process of treating silk containing its natural gum, which comprises soaking about 100 parts of the silk for about 30 minutes at room temperature in about 400 parts of a bathcontaining 5 parts of a papain preparation,- 4 parts of sulfonated oil, 0.05 parts of potassium cyanide and 2 parts of monosodium phosphate, removing the silk from the bath, centrifuging and then drying, said parts being by weight.

7. A process of treating silk containing its natural gum, which comprises immersing 100 parts of said silk for 30 minutes at room temperature in 400 parts of an aqueous bath, the bath containing 5 parts of a pancreati'n preparation and 1 part of sodium sulfite, removing the silk from the bath, centrifuging and air drying, said parts being by weight.

8. The process of treating raw silk coated on covered with its natural gum, without removing or destroying said natural gum, so that its gum may be more readily removed subsequently, which process comprises impregnating the silk with a proteolytic enzyme solution, at such a temperature and for such a length of time as to pre vent removal of the gum, drying the impregnated silk without removal of any substantial amount of the gum, subjecting the silk to textile processing and then removing the gum from the textile thusformed by immersing the textile in a degumming bath.

9. As a new article of manufacture, a substantially dry silk containing substantially all of its gum which silk has been impregnated with a gum modifying proteolytic enzyme preparation and which silk possesses substantially the appearance and weaving properties of untreated silk containing its natural gum, which impregnated gum is in such modified form that it can be substantially and readily removed by treatment with hot water. LEO WALLERSTEIN. THOMAS HAWLEY. ROWLAND A. GALE. 

